Google's clash with China is about much more than the fate of a single, powerful firm. The company's decision to pull out of China, unless the government there changes its policies on censorship, is a harbinger of increasingly stormy relations between the US and China.

The reason that the Google case is so significant is because it suggests that the assumptions on which US policy to China have been based since the Tiananmen massacre of 1989 could be plain wrong. The US has accepted – even welcomed – China's emergence as a giant economic power because American policymakers convinced themselves that economic opening would lead to political liberalisation in China.

If that assumption changes, American policy towards China could change with it. Welcoming the rise of a giant Asian economy that is also turning into a liberal democracy is one thing. Sponsoring the rise of a Leninist one-party state, that is America's only plausible geopolitical rival, is a different proposition. Combine this political disillusionment with double-digit unemployment in the US that is widely blamed on Chinese currency manipulation, and you have the formula for an anti-China backlash.